Chinese President Xi Jingping warned President Joe Biden not to “play with fire” over Taiwan in a two hour call Thursday between the two leaders. Xi’s comments came as House Speaker Nancy Pelosi departed for a tour of Asia Friday, where a possible visit to Taiwan remains uncertain.

“Those who play with fire will perish by it,” Xi said according to the Chinese Ministry of Foreign Affairs. “It is hoped that the U.S. will be clear-eyed about this.”

The Chinese leader has maintained the “One China” policy, refusing to accept Taipei’s independence. On the other hand, the United States has committed to defending Taiwan’s interests, despite the official stance in the matter being neutrality.

The White House addressed the conversation about Taiwan, saying the President “underscored that the United States policy has not changed and that the United States strongly opposes unilateral efforts to change the status quo or undermine peace and stability across the Taiwan Strait.”

Pelosi plans to visit Japan, South Korea, Malaysia and Singapore during her trip to the region. While it wouldn’t be unprecedented for the House Speaker to make a detour to Taiwan, it could further strain the already contentious U.S.-China relationship.

White House Press Secretary Karine Jean-Pierre was asked about the President’s thoughts on the matter and referenced his time as a Senator during a Thursday press briefing.

“He understands this process,” she said in response to a question. “You do not tell a congressional member where they can or cannot go. He believes that this is up to the speaker to decide. And also, let’s be very clear, there is no trip that has been announced.”

Xi and Biden have both been invited to the next G20 summit of the world’s largest economies in Indonesia in November, which could possibly result in a face to face meeting. Xi has only left mainland China once since the start of the COVID-19 pandemic, making it unclear whether he will make that journey.

The Associated Press and Reuters contributed to this report.